1. Field of the Invention
The present invention relates in general to an electrical connector for wires and, more particularly, to a push-in connector for connecting multiple wires electrically together.
2. Description of the Related Art
Push-in wire connectors are useful for connecting multiple wires electrically together in applications including providing utility power gridwork for homes and offices, etc. U.S. Pat. No. 4,824,395 “Push-in wire connector” to Blaha, for example, disclosed a wire connector having a conductive clip of relative simple design for easy fabrication. The clip responsible for providing electrical connection between the connected wires was enclosed in a housing. The clip was made in the form of a cantilever spring so that a wire inserted through an aperture in the housing can deflect the spring and be clamped and retained in the housing. Blaha's wire connector, though simple and easy to manufacture, required its single piece clip to provide both good electrical conduction between and firm mechanical retention of the wires to be electrically connected together.
Such a dual-role requirement placed limitation to the selection of suitable metallic or alloy material for clips, resulting in the necessity of a compromise between electrical conduction and mechanical retention strength characteristics required for the application. U.S. Pat. No. 6,257,919 “Electrical connector with improved locking means” to Cutler et al. disclosed a connector aimed at improved locking interconnection between the connected wires and the connector. Cutler et al. proposed an electrical contact component accommodated inside an enclosure with at least two spring locking clips. The contact component served to provide the electrical conduction between all the wires to be connected, while the spring locking clips were responsible for the mechanical retention of the connected wires.
The wire connector by Cutler et al. avoided the problem of the use of a dual-role metallic or alloy material optimized for both electrical conduction and mechanical strength for its contact component. However, since the contact component also constituted the main and bulk metallic structure for the connector, an optimized material such as copper alloy for the contact component can still be costly for the connector. U.S. Pat. No. 6,746,286 “Push-in wire connector” to Blaha was able to alleviate this cost-performance problem by introducing a busbar in the form of, rather than serving as the main metallic structure, a contact plate having the minimum required size for good electrical conduction between the wires to be connected.
However, all these prior wire connectors failed to simultaneously provide good electrical conduction and ease of use while being cheap and simple to manufacture. For example, while the connector by Cutler et al. provided good mechanical wire retention characteristics and Blaha's busbar-equipped connector achieved improved electrical conduction for the connected wires, all failed to consider the true ease of use. As a wire to be connected by any of these connectors is pushed in, the stripped wire end inserted tends to be bent or deflected sideways since the leg of the resilient clip presents a considerable resistance to the insertion of the wire end. The resistance becomes stronger as the clip is made more resilient to ensure good mechanical retention of the wire.
Although the connector by Cutler et al. did include parallel guide ribs to assist in holding wire end in the correct orientation during insertion, however, vertical height of these ribs were insufficient that there were still the possibility of wire end sideway deflection or bending to result in failed insertion. This is particularly a problem in the case of multi-threaded wires.
Blaha's busbar connector was not free of this problem as well. The Blaha connector included rear receptacles for receiving the ends of the inserted wires, however, these receptacles were not helpful at all in preventing the sideway deflection or bending of the wire end during the insertion. They only serve to provide a space for receiving the wire end—after a successful insertion. Neither were the extensions in the Blaha busbar connector of any substantial assistance in preventing the deflection or bending of the inserted wire ends since their primary goal was to hold the busbar in place and they were positioned way behind the point of pressed contact between the legs and the wires along the direction of wire insertion.